Field of the Invention
The invention relates to a honeycomb structure including at least partially textured films so that ducts through which a fluid can flow and that have a pitch and a wave height are formed, adhesive and a powderous brazing material being provided in regions of contact between the films, within an adhesive strip width, and to a method for applying adhesive and brazing material to such a honeycomb structure.
Such honeycomb structures are used, in particular, as catalytic converter carrier bodies in exhaust gas systems of mobile internal combustion engines (for example, spark ignition engines or diesel engines or the like). Honeycomb bodies and a method for manufacturing them are disclosed, for example, in European Patent 0 422 000 B1, corresponding to United States Patent Publication Nos. 2002/0129890 and 2001/0013390, or German Published, Non-Prosecuted Patent Application DE 29 24 592, corresponding to U.S. Pat. No. 4,521,947 to Nonnenmann et al. and U.S. Pat. No. 4,381,590 to Nonnenmann et al. The latter describes a carrier matrix for a catalytic reactor for emission control of an internal combustion engine of a vehicle, which matrix is formed from high-temperature-proof steel plates. The carrier matrix is coated with a catalytic material, the steel plates being embodied as smooth and corrugated plates and being disposed alternately in layers.
With respect to the manufacturing method of such a carrier matrix, it is proposed that the steel plates, firstly, be degreased and/or pickled. The steel plates are, then, provided with a brazing material coating before they are disposed alternately in layers. Adhesive or brazing material can, then, be applied to the smooth steel plates, the corrugated steel plates or both types of steel plate. Brazing material is applied in strips in the direction of the corrugations of the corrugated steel plates, or perpendicularly thereto. After the steel plates have been stacked and wound to provide a carrier matrix, the carrier matrix is heated and all the layers or steel plates are simultaneously brazed to one another. A multiplicity of shapes and configurations of the steel plates with respect to one another are already known (S-shaped, spiral, etc.), reference being made in this respect, for example, to European Patent 0 430 945, corresponding to U.S. Pat. Nos. 5,139,844, 5,135,794, and 5,105,539 to Maus et al., or EP 0 436 533, corresponding to U.S. Pat. No. 5,102,743 to Maus et al.
Such a method has proven very satisfactory in the past, but has disadvantages, particularly with respect to the costs and the brazing quality. Although the provision of adhesive or brazing material in the form of strips already entails a reduction in the adhesive or brazing material that is used for manufacture, excessively rigid connection of the steel plates to one another, which is not desired in certain cases has, nevertheless, been detected within the scope of load testing. In this context, it has also been discovered that, particularly when very thin steel plates are used, it is important not to introduce too much brazing material material into the carrier matrix because an excessive quantity of brazing material results in an increased risk of corrosion during the use of such a carrier matrix in the exhaust gas system of motor vehicles. Furthermore, the excessive provision of brazing material constitutes a cost factor that has to be allowed for, in particular, within the scope of large-scale manufacture.
A further manufacturing problem occurs when the steel plates are stacked or wrapped. Because the brazing material is already applied before the stacking or wrapping, it may also come to be disposed in the contact regions between the corrugated steel plate and the smooth steel plate so that direct contact between these plates is not ensured. During subsequent thermal treatment, the adhesive vaporizes at least partially and the brazing material melts so that gaps are formed under certain circumstances. This may result in a situation in which a joint connection between steel plates that are disposed adjacent to one another is not formed continuously over the desired connecting region. This has an appreciable influence on the fatigue strength of such a carrier matrix when the latter is subjected to thermal and dynamic conditions in the exhaust gas system of a mobile internal combustion engine.